Sudong Yang

Magnetic graphene foam for efficient adsorption of oil and organic solvents

This paper reported the preparation of magnetic graphene foam loaded with magnetite (Fe3O4) nanoparticles and its application for the adsorption of oil and organic solvents. The foam with porous and hierarchical structures was derived from graphene oxide film reduced by gaseous reduction in a hydrothermal system. Drastically different morphologies of Fe3O4 nanoparticles with nanosheet arrays or cubic structures were observed on graphene foam by controlling the reduction degree of graphene oxide under mild conditions. Benefiting from the integration of porous structures and magnetic properties, the graphene foam manifests outstanding oil adsorption capacity, high restoration for absorbates as well as excellent recyclability and stability under cyclic operations. The simple and effective strategy for the preparation of graphene foams developed in this study may offer a new alternative for scale-up production of graphene materials used for the cleanup of oil spills.

Low cost carbon fiber aerogel derived from bamboo for the adsorption of oils and organic solvents with excellent performances

This paper reports the preparation of multi-functional carbon fiber (MCF) aerogel by a simple hydrothermal and carbonization process using disposable bamboo chopsticks. The developed material manifested dramatic multi-functionalities, including excellent flexibility under the mechanical compression, efficient capability to separate oily droplets from water, and high adsorption capacity for a variety of oils and organic solvents by up to 129 times of its own weight. Moreover, the MCF aerogel can be recycled for many times by distillation, combustion or squeezing, making the material satisfy the requirements for oil–water separation in practice. Coupled with economical, environmentally benign manufacturing process, sustainability of precursor and versatility of material, the MCF aerogel developed in this study will be a promising candidate to address the problems arising from the spills of oily compounds.

Ternary silicone sponge with enhanced mechanical properties for oil–water separation

Silicone sponges have been developed and applied over the years for the separation of oil–water mixtures. However, the materials suffer from a poor mechanical performance under cyclic operations. In this work, we report the preparation of ternary silicone sponges via a facile sol–gel process using methyltrimethoxysilane (MTMS), dimethyldimethoxysilicane (DMDMS) and tetraethylorthosilicate (TEOS) as precursors. Special emphasis is put on illustrating the role of TEOS on the morphology, mechanical and thermal properties of the developed silicone sponge. The results show that the introduction of TEOS into the binary silicone sponge resulted in a higher degree of crosslinking reactions, as verified by the chain-like structures in the sample, and the much enhanced mechanical properties and thermal stability of the material. More importantly, the optimized ternary sponge displayed a stable superhydrophobicity, a high efficiency for separating various organic liquids from water, and an excellent recyclability under cyclic operations. The excellent structural and thermal stability of the optimized sponge make it an ideal candidate to be used in the separation industry and for environmental remediation.

Graphene foam with hierarchical structures for the removal of organic pollutants from water

Porous materials with hierarchical structures are of increasing importance because of their potential application in separation and electronic technology. Herein, three-dimensional graphene foam (GF) was prepared by using polystyrene particles as a sacrificial template and an autoclaved leavening process, and the GF was further processed by carbon dioxide as an activation agent to produce meso- and nano-pores in the foam. The resulting hierarchical graphene foam (HGF) exhibits high porosity, hydrophobicity and excellent thermal stability. Compared to regular GF, due to the integration of hierarchically porous structures, HGF manifests outstanding performance for oil adsorption when applied to separating oil–water mixtures, through a combination of hydrophobicity and capillary action.

Three-dimensional titanium dioxide/graphene hybrids with improved performance for photocatalysis and energy storage

A series of three-dimensional (3-D) TiO2/graphene (TiO2/GR) hybrids with different TiO2 weight ratios were prepared using a self-assembly approach followed by the gaseous reduction in a hydrothermal system. The method was based on the electrostatic attraction between the positively charged titanium glycolate precursor and negatively charged graphene oxide in an aqueous medium without any surfactant or template. The structure, morphology, physical and optical properties of the as-synthesized hybrids were characterized, and the results showed that TiO2 spheres were homogeneously confined within the 3-D networks of graphene, and acted as pillars to effectively separate the graphene sheets from each other. By optimizing the ratio of TiO2 in the hybrids, the material was identified as an excellent photocatalyst to remove organic compound in water with high degradation efficiency. Additionally, TiO2/GR hybrids delivered high specific capacity, enhanced rate capability and excellent cyclic stability when used as a freestanding electrode for lithium ion batteries.

Surface roughness induced superhydrophobicity of graphene foam for oil-water separation

Surface free energy and roughness are two predominant factors governing the hydrophilicity/hydrophobicity of materials. This paper reported the surface roughness induced hydrophobicity of graphene foam by incorporating silica nanoparticles onto graphene sheet via a sol-gel method and subsequent modification using silane. Various techniques were employed to characterize the morphology, composition and surface properties of sample. The results showed that the as-prepared graphene foam exhibited a superhydrophobic surface with a high water contact angle of 156°, as well as superoleophilicity with excellent adsorption capacities for a variety of oil compounds. Benefiting from the integration of enhancement on the surface roughness and reduction on the surface free energy of material, the graphene foam developed in this study had the capability to effectively separate oil-water mixture with excellent stability and recyclability.